Optical polymer element for coupling photoelements onto integrated-optical circuits

ABSTRACT

An integrated-optical device in polymer technology, having a photoelement coupled onto an optical waveguide, with only the evanescent field components of the optical waveguide being coupled by an optical coupling element into the photoelement, wherein the photoelement (23) is incorporated into a polymeric upwardly closed cover plate (51), the cover plate (51) is fitted exactly onto a base plate (50) having an optical waveguide (20), and the coupling element is an optical buffer layer (54) disposed between the cover plate (51) and base plate (50). Preferably, the buffer layer (30) has a refractive index in the region opposite the photoelement (23) which is less than or equal to the refractive index of the optical waveguide (20), but greater than the refractive index of the buffer laser (30) outside the region opposite the photoelement (23).

The invention relates to an optical polymer element according to thepre-characterizing clause of the main claim and is preferably used inthe coupling of suitable photodiodes onto devices of integrated optics.

The increasing use of integrated-optical components for opticalcommunications, for sensor technology and the computer field lends evergreater significance to the optical connection technique.

Devices of integrated optics (IO) for optical communications (wavelengthrange 1300 to 1550 nm) and for optical sensor technology (usually in thewavelength range of 633-850 nm) require an optoelectronic signalconversion at the interface between optical and electronic signalprocessing. This takes place, for example, by coupling the signal lightinto a photodiode of corresponding spectral sensitivity (for example,InP compounds for optical communications, Si photodiodes for sensortechnology).

The usual way of coupling a photodiode onto an optical waveguideconsists in a direct coupling of the photodiode onto the waveguide end("butt coupling"). The light-energy is in this case guided completelyinto the diode and is transformed there into states of electronicexcitation. In addition, an optical waveguide can also be coupled weaklyto a photodiode, by only its evanescent field components transferringinto the diode ("leaky wave coupling")--the magnitude of the electronicsignal response is in this case a function of coupling strength andcoupling length. Alternatively, furthermore, an optical waveguide can bepassed through an optical semiconductor amplifier (essentially asemiconductor laser diode with antireflection-coated end faces) and thedecrease in the charge carrier inversion can be picked off as anelectronic signal via the external power supply of the amplifier diode.

The known devices have the disadvantage that they can only be producedin a relatively complex manner.

SUMMARY AND ADVANTAGES OF THE INVENTION

The optical polymer element according to the invention offers incomparison with the known devices, the coupling and fastening ofphotoelements onto integrated-optical polymeric waveguides is possible,the polymer element is compatible with planar-integrated electronics andgreat cost advantages are achieved by mass production.

For this purpose, a coupling element, preferably a buffer layer, isprovided between the optical waveguide and the photoelement, the bufferlayer having, in the region of the photoelement, a refractive indexwhich is less than or equal to the refractive index of the opticalwaveguide, but is greater than the refractive index of the buffer layeroutside the region of the photoelement.

Further advantageous developments are specified in the sub-claims.

A preferred solution is if the photodiodes are integrated by planar andmonolithic techniques directly into suitable substrates (for examplesilicon) by diffusing processes and/or ion implantation. The electricalwiring is advantageously performed directly on the chip. To applyoptical waveguides onto a chip electronically processed in this way,first of all an optical buffer layer of lower refractive index than thelight-guiding layer is applied. This is followed by the light-guidingpolymer layer with the laterally structured optical waveguides and,optionally thereover, an upper covering layer of lower refractive index.If the buffer layer is optically thin (thickness<1/e drop of the fielddistribution), the evanescent field components extend into the substrateand result in strong intensity losses. If, conversely, the buffer layeris optically thick (thickness>>1/e drop of the field distribution), evenin the region of the photodiode there is no light coupled in to thelatter.

The necessary high and local coupling of the optical waveguide onto thephotodiode is thus achieved by virtue of the fact that the "opticallyinsulating" buffer layer can be optically changed locally over thesensitive window of the photodiode in such a way that the evanescentfields can extend locally far beyond the buffer layer (and into thephotodiode). For this purpose, the buffer layer can be masked in such away that a local ion diffusion or ion implantation raises only therefractive index in a desired window over the photodiode. The masking isremoved after the process and the optical-waveguide and covering layerapplied. The degree of coupling of the optical waveguide can be set bymeans of the index change in the buffer layer.

An advantageous possibility for realization is offered by a polymerlayer (for example PMMA as the optical buffer) with photopolymerizableadditives (for example benzil dimethyl ketal). Here, the refractiveindex of the buffer layer can be raised locally over the photodiode bysimple UV exposure with the masking technique. By UV exposure ofstructures of varied density (neutral wedge), the index can additionallyalso be gradually changed spatially, if index jumps and possiblyresulting disturbances of the single-mode emission of the waveguide areto be avoided. Depending on the photopolymerization behaviour of theoptical buffer, in this case either an index profile of the buffer inthe longitudinal direction of the waveguide can be produced (i.e.slightly increased refractive index at the edges of the photodiode, moreincreased index over the detection window of the diode) or a spatialdepth profile of the index increase in the buffer layer (i.e.superficial index increase at the diode edges, deeper-extending indexincrease over the detection window of the diode=>"a vertical taper") canbe produced.

In both limiting cases (combinations are possible), the slightly raisedrefractive index over the photodiode effects there a weaker guidance ofthe light, synonymous with a broadened field distribution in thedirection of the diode. By adiabatic index changes (for example neutralwedge exposures), in this case the disturbance of the guiding propertiesis kept sufficiently small in order to preserve the single-mode emissionof the waveguide--this is important if the signal is to be looped pastthe photodiode (and merely attenuated by the detection) or if the signalis to be coupled wavelength-selectively into optical resonators, withoutmassively influencing the mode distribution in the resonator.

The buffer layer can itself, in addition, also be laterallyphotostructured, by a taper structure running to a point and having aslightly increased index being exposed into it. In this case also, thelight field of a waveguide lying thereover is expanded gradually (byadiabatic activating of the disturbance) downwards in the direction ofthe diode by the index manipulation of the buffer layer. If therefractive index of the buffer layer in the tapered region is even sethigher than that of the optical waveguide lying thereover, the lightfield is drawn completely out of the waveguide and fed to the diode.

Following the index manipulation of the buffer layer, as describedabove, the optical waveguide is structured in the layer lying thereover.What is important here is the possibility in principle of providing anypreprocessed and wired electronic chips subsequently with a polymeric"optical connection level" over it, which can be performed withoutdisturbance of the electronic devices on account of the low processtemperatures necessary for the production of polymeric opticalwaveguides.

According to the invention, it is furthermore advantageous if opticalwaveguides are predefined in the form of small, precision-made grooveson a "master structure" and are further processed by an electroformingtechnique for use as a mould (tool) for injection-moulding orinjection-compression moulding processes. Consequently, amass-producible duplication of optical waveguide devices becomespossible. The small grooves in the embossed "daughter structures"(polymer substrates) are filled with higher-refractive-index opticalpolymer for the production of a solid-polymer device (channel waveguide)and are closed at the top by a polymeric (lower-refractive-index) coverplate (superstrate). The cover plate may, for example, consist of thesame material as the waveguide daughter structures and then define apassive device. The cover plate may, however, also carry electronicdevices used in hybrid form (for example photodiodes), which can then beoptically coupled onto the optical waveguides. For this purpose, asuitable master structure with receiving openings for the electronicdevices is produced for the cover plate. This can be performed byanisotropic precision etching of receiving depressions in silicon wafersor else by so-called X-ray gravure lithography in PMMA materials. Thecovering structures can be electro-formed from this like the opticalwaveguides and duplicated in injection-moulding/injection-compressionmoulding processes.

The photodiodes (and, if appropriate, further devices) are insertedindividually (or preferably as a detector array) into the depressions ofthe cover plate and fastened. Before the exact fitting together of thethus-prepared cover plate and the base plate with the optical waveguides(in the form of small grooves with filled, higher-refractive-indexliquid polymer), there must be incorporated between the opticalwaveguides and the electronics in the cover plate an optical bufferlayer, which allows an optical coupling via the evanescent fieldcomponents only in the region of the diode entry windows.

Two advantageous ways are appropriate for this:

a) The electrical wiring of the electronics is performed by depositingcorresponding conductor tracks on the equipped cover plate. A polymerlayer (index as cover plate) with photopolymerizable admixtures isapplied thereover as the optical buffer. By local UV exposure (maskingtechnique), the index can be set in the region of the photodiode, asdescribed above, with or without taper structures in such a way that thelight coupling is possible here--and only here--in the ready-assembleddevice.

b) The production of the electrical conductor tracks is performed on oneside of a thin polymer film. This must be suitable as an optical bufferlayer, i.e. have low attenuation and a refractive index less than thatof the optical waveguides (optical film thickness>>1/e drop of theoptical fields). The film could, for example, consist of the samematerial from which daughter structures and covering structures are alsoproduced. In the case of thicknesses in the μm range, this film ispreferably first of all stabilized by a carrier film.

The bufferfilm is laminated with the electrical conductor tracks on tothe cover plate, in order in this way to ensure a contacting of theelectronic assemblies (after that, the rear carrier film can be pulledoff).

The refractive index of the buffer film can then be raised again locallyin the region of the diode windows by diffusion or implantationprocesses or by uv exposures (if there are correspondingly crosslinkableoligomers in the film) and consequently the coupling degree can be set.The various possibilities of lateral and vertical tapering are againavailable.

It is also possible, however, in an advantageous way for a thermoplasticfilm to be hot-embossed in the region of the diode windows by means of acorrespondingly shaped embossing tool. This results in a layer thicknessof the optical buffer which is defined by the embossing tools and isslightly thinner locally and ultimately results in a stronger fieldcoupling in the desired regions. The field distributions are in turncomparable with the already mentioned qualitative variations.

Subsequently, the complete device is fitted exactly together, so thatthe photodiode windows come to lie exactly over the associated opticalwaveguides. The higher-refractive-index polymer in the optical waveguidegrooves may in this case be formed as a thermally or UV-crosslinkingadhesive and thus ensure the mechanical connection of the assemblies. Atthe same time, this liquid polymer compensates for any possibledifferences in thickness with respect to the cover plate, for example inthe case of embossed buffer films. The buffer film may protrude with itsapplied conductral tracts laterally beyond the cover plate and permitsimple electrical contacting to the outside.

It is furthermore in the spirit of the invention if an optical waveguidewhich has been produced, for example, by local photopolymerization, byso-called "UV bleaching" or by some other structuring technique in anorganic polymer film is coupled onto the photodiode by an opticallyhigher-refractive-index, transparent adhesive (for exampleUV-polymerizing adhesives). The said photodiode is located with itsphotosensitive side directly over the upwardly non-covered opticalwaveguide. The degree of optical coupling can be set by choice of therefractive index, the thickness and the surface area (length in thedirection of the waveguide) of the polymer adhesive. Depending on thedegree of coupling, the light can be coupled out of the opticalwaveguide (and in the loss-free limiting case coupled into thephotodiode), or else be only slightly attenuated, in order for exampleto pick off signals from a data bus without influencing its opticaltransparency. A suitable coupling distance can be set by the shaping ofthe diode. The optical adhesive serves at the same time both for theoptical coupling and for the mechanical fixing. The entire chip can besubsequently encapsulated and protected by a lower-refractive-indexcovering layer.

Examples of applications which may be mentioned are integrated-opticaldisplacement/angle sensors or communication receiver stations, whichthus can be assembled in an inexpensive way. In the case of awavelength-selective detection, the signals would have to be filteredout here by wavelength-selective couplers or integrated-opticalresonators on the optical chip and fed to the photoreceiver.

BRIEF DESCRIPTIONS OF THE DRAWINGS

The invention is to be explained in more detail below in exemplaryembodiments with reference to the associated drawings, in which:

FIG. 1 perspectively shows the basic coupling of a photodiode;

FIG. 2 shows a section through the coupling location according to FIG.1;

FIG. 3 shows a coupling location on a further example in plan view;

FIG. 4 shows a section through the coupling location according to FIG.3;

FIG. 5 shows a coupling location according to FIG. 3 with a taperedbuffer region;

FIG. 6 shows a section through the coupling location according to FIG.5;

FIG. 7 perspectively shows a polymeric waveguide device before assembly;

FIG. 8 shows a section through the polymeric waveguide device accordingto FIG. 7 in the assembled state;

FIG. 9 perspectively shows a polymeric waveguide device with integratedphotodiode before assembly;

FIG. 10 shows a section through the polymeric waveguide device accordingto FIG. 9 in the assembled state;

FIG. 11 perspectively shows a further polymeric waveguide device withintegrated photodiode before assembly;

FIG. 12 shows a section through the polymeric waveguide device accordingto FIG. 11 in the assembled state;

FIG. 13 shows a section through a further polymeric waveguide devicewith integrated photodiode and

FIG. 14 shows a section through a further polymeric waveguide devicewith integrated photodiode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In all the figures, the same parts, including parts which are the sameby analogy, are denoted by the same reference numerals.

FIG. 1 shows an optical waveguide 20 which is arranged in a polymer film22 provided on a substrate plate 21. A photodiode 23 is adhesively fixedonto the optical waveguide 20 by means of a polymer adhesive 24.

In FIG. 2 it becomes clearer that the photodiode 23 has a certaindistance from the polymer film 22 and consequently from the opticalwaveguide 20. This distance is determined by the spacers 25. A bufferlayer 26 is provided between substrate plate 21 and polymer film 22. Thephotodiode 23 is arranged with its photosensitive side directly over theoptical waveguide 20. The entire device is encapsulated by a coveringlayer 27. The following relationships apply for the refractive indicesof the individual component parts:

The refractive index n₀ of the covering layer 27 and the refractiveindex n₄ of the buffer layer 26 are less than or equal to the refractiveindex n₃ of the polymer film 22. The refractive index n₁ of the opticalwaveguide 20 is greater than n₃. The refractive index n₂ of the polymeradhesive 24 is less than or equal to the refractive index n₁ of theoptical waveguide 20.

The mode of operation in principle is as follows:

A light pulse conducted through the optical waveguide 20 is coupled outof the optical waveguide 20, partially or completely depending on use,according to the set refractive index and also the thickness and lengthof the polymer adhesive 24, and is fed to the photodiode, which performsits predetermined function there. The spacers 25 may be metal surfaceswhich are applied to the photodiode 23 and increased to the desiredthickness (=spacing), for example by electroplating, which at the sametime serve as conductor tracks for passing on the signal to thephotodiode 23.

The example shown in FIGS. 3 and 4 comprises a photodiode 23 which isintegrated in a substrate plate 21 and over which the optical waveguide20 runs, separated by a buffer layer 30. The buffer layer 30 has aregion 31 which is arranged directly between the optical waveguide 20and the photosensitive window of the photodiode 23.

The following relationships apply for the refractive indices:

The refractive index n₀ of the covering layer 27 is less than or equalto the refractive index n₃ of the buffer layer 30, which in turn is lessthan the refractive index n₂ of the region 31, which is less than therefractive index n₁ of the optical waveguide 20. In 32, the qualitativefield distribution outside the region 31 is shown. The light pulse isguided within the optical waveguide 20. The qualitative fielddistribution in the region 31, here denoted by 33, makes it clear that,due to the higher refractive index of the buffer layer 30, theevanescent field components locally extend far beyond the buffer layer30, and consequently into the photosensitive window of the photodiode23. Consequently, the intended detection function of the photodiode 23is initiated.

In FIGS. 5 and 6 it is shown in a preferred exemplary embodiment with ananalogous construction according to FIGS. 3 and 4 how the region 31 istapered. On the left-hand side, a vertical taper is diagrammaticallyshown in 40 and on the right-hand side a lateral taper isdiagrammatically shown in 41 (in actual devices, either the one or theother taper form is then used on both sides of the diode).

In the region 40, the taper has a slightly increased refractive index atthe edges of the photodiode 23 and a more increased refractive indexover the photosensitive window of the photodiode 23. The variation ofthe refractive index is indicated by the line 42. The taper may,however, also have a laterally pointed profile, as shown in the region41. Here, the refractive index decreases in the lateral direction untilthe taper comes to a point outside the photodiode 23. Regarding therelationships between the refractive indices and the qualitative fielddistribution, the same applies as already stated with respect to FIGS. 3and 4.

The further examples relate to solid-polymer devices produced by aforming technique.

The basic construction of solid-polymer devices is clearly illustratedin FIGS. 7 and 8. Higher refractive-index optical polymers, which formthe optical waveguide 20, are cast in a base plate 50 of polymersubstrate in precision-fabricated sizes. The base plate 50 is coveredover by a cover plate 51, which may consist of the same polymersubstrate as the base plate 50. The connection takes place by means of aliquid polymer 52, which may be identical to the polymer of the opticalwaveguide 20.

As shown in FIGS. 9 and 10, a photodiode 23 is inserted into adepression 53 of the cover plate 51. An optical buffer layer 54 isarranged between the base plate 50, or the adhesive 52, and the coverplate 51. The optical buffer layer 54 has a region 55 which allows acoupling between the optical waveguide 20 and the photodiode 23 only inthis region. The region 55 may in turn be formed as already the region31, described in FIGS. 3 to 6, that is to say without or with taperstructures. The electrical connection tracks 56 of the photodiode 23 areled to the outside on the equipped cover plate 51.

The refractive indices of the individual regions behave analogously tothose described in FIGS. 1 to 4, the refractive indices of substrateplate 50 and cover plate 51 being less than or equal to the refractiveindex of the buffer layer 54.

A light pulse coming through the optical waveguide 20 acts with itsevanescent field components in the region of the photoactive window ofthe photodiode 23, and only here, through the buffer layer 54 andinitiates in the photodiode 23 the desired switching function, which canbe picked off via the connection tracks 56.

A further example is represented in FIGS. 11 and 12. The electricalconnection tracks 56 of the photodiodes 23 are applied on a thin polymerfilm, which at the same time serves as optical buffer layer 54. Beforeassembly, the film is laminated with an exact fit onto the cover plate51. All further component parts and functions have already beendescribed in detail with respect to the other examples.

The example according to FIG. 13 has an optical buffer layer 54 in theform of a film, as described in FIGS. 11 and 12, which has been embossedin the region of the photoactive window. The embossing has been carriedout in such a way as to obtain a region 60 which gives a locally definedslightly thinner layer thickness of the buffer layer 54. By the settingof this layer thickness, the coupling of the photodiode 23 onto theoptical waveguide 20 is set in the manner already described.

In a further development, as shown in FIG. 14, apart from the describedindex manipulation of the buffer layer 54, which makes the latter"optically thinner" and consequently transmissive for the light waves,the light entry surface of the photodiode 23 can also be broughtgeometrically closer to the optical waveguide. For this purpose, thephotodiode structure, in the example an InP-based technology isdescribed without restricting generality, may be provided selectivelyover the light entry window with an InP covering layer 70 grown over it,which may typically be 0.2 to 1 μm thick. If a planarizing polymerbuffer 54 is applied over such a diode structure and the opticalwaveguide 20 is applied thereover, the buffer action in the region ofthe diode entry window is distinctly reduced and, owing to the higherrefractive index of the semiconductor materials (typically n>3.5), theevanescent light is drawn out of the optical waveguide and fed to thelight-sensitive p/n junction of the semiconductor diode for detection.

This geometrical effect of the photodiode, which extends into the bufferlayer, can be combined in the sense already described additionally withphotopolymerized, tapered structures in the buffer layer.

I claim:
 1. An Integrated-optical device in polymer technology, having aphotoelement coupled onto an optical waveguide, with only the evanescentfield components of the optical waveguide being coupled by an opticalintermediate element into the photoelement, and wherein: thephotoelement is incorporated into a polymeric upwardly closed coverplate; the cover plate is fitted exactly onto a base plate comprising apolymer layer having a light guiding optical waveguide; the intermediateelement is an optical buffer layer disposed between the cover plate andthe base plate; and the entire buffer layer has a lower refractive indexthan the lightguiding polymer layer.
 2. An integrated-optical deviceaccording to claim 1, wherein the buffer layer is optically changedlocally over a sensitive window of the photoelement such that theevanescent light fields extend locally far beyond the buffer layer andinto the photoelement.
 3. An integrated-optical device according toclaim 1, wherein the refractive index of the buffer layer is raised, bylocal ion diffusion or ion implantation, in the region of a sensitivewindow of the photoelement.
 4. An integrated-optical device according toclaim 3, wherein the degree of optical coupling is set via the height ofthe index change of the buffer layer.
 5. An integrated-optical deviceaccording to claim 1, wherein a polymer layer with photopolymerizableadditives, the refractive index of which is set locally over a sensitivewindow of the photoelement by UV exposure, is used as the buffer layer.6. An Integrated-optical device in polymer technology, having aphotoelement coupled onto an optical waveguide, with only the evanescentfield components of the optical waveguide being coupled by an opticalintermediate element into the photoelement, and wherein: thephotoelement is incorporated into a polymeric upwardly closed coverplate; the cover plate is fitted exactly onto a polymeric base platehaving an optical waveguide; the intermediate element is an opticalbuffer layer disposed between the cover plate and base plate; the bufferlayer is a polymer layer with photopolymerizable additives responsive toUV exposure and whose refractive index is set locally in a regionopposite a sensitive window of the photoelement; the refractive indexgradually changes spatially due to UV exposure, in varied density, suchthat the refractive index profile of the buffer layer is set in alongitudinal direction of the waveguide or as a spatial depth profile ofa refractive index increase over the sensitive window of thephotoelement.
 7. An Integrated-optical device in polymer technology,having a photoelement coupled onto an optical waveguide, with only theevanescent field components of the optical waveguide being coupled by anoptical intermediate element into the photoelement, and wherein: thephotoelement is incorporated into a polymeric upwardly closed coverplate; the cover plate is fitted exactly onto a base plate comprising apolymer layer having a light guiding optical waveguide; the intermediateelement is an optical buffer layer disposed between the cover plate andthe base plate; and the buffer layer is structured in the lateraldirection in a region opposite a sensitive window of the photoelement bya taper structure having a slightly increased refractive index.
 8. Anintegrated-optical device according to claim 7, wherein the taperstructure runs to a point.
 9. An integrated-optical device according toclaim 1, wherein the optical buffer layer allows an optical couplingwith the optical waveguide only in a region of a sensitive window of thephotoelement.
 10. An integrated-optical device according to claim 1,wherein the optical waveguides comprise higher-refractive-index polymersincorporated in structures formed as grooves in the polymeric baseplate.
 11. An Integrated-optical device in polymer technology, having aphotoelement coupled onto an optical waveguide, with only the evanescentfield components of the optical waveguide being coupled by an opticalintermediate element into the photoelement, and wherein: thephotoelement is incorporated into a polymeric upwardly closed coverplate; the cover plate is fitted exactly onto a base plate comprising apolymer layer having a light guiding optical waveguide; the intermediateelement is an optical buffer layer disposed between the cover plate andthe base plate; the optical buffer layer, with photopolymerizableadmixtures, is applied to the cover plate; and the refractive index ofthe buffer layer in a region opposite a sensitive window of thephotoelement is raised and set in at least one of the longitudinaldirection of the waveguide, as a spatial depth profile of the refractiveindex increase, and as a taper structure by local UV exposure.
 12. AnIntegrated-optical device in polymer technology, having a photoelementcoupled onto an optical waveguide, with only the evanescent fieldcomponents of the optical waveguide being coupled by an opticalintermediate element into the photoelement, and wherein: thephotoelement is incorporated into a polymeric upwardly closed coverplate; the cover plate is fitted exactly onto a base plate comprising apolymer layer having a light guiding optical waveguide; the intermediateelement is an optical buffer layer disposed between the cover plate andthe base plate; and the optical buffer layer is formed as a thin polymerfilm having electrical conductor tracks on a side facing the coverplate; and this buffer film with the electrical conductor tracks islaminated onto the cover plate such that the photoelements areelectrically contacted at the same time.
 13. An integrated-opticaldevice according to claim 12, wherein the refractive index of the bufferfilm is raised locally in the region opposite a sensitive window of thephotoelement.
 14. An integrated-optical device according to claim 12,wherein the degree of optical coupling is set via the refractive index.15. An integrated-optical device according to claim 13, wherein therefractive index of the buffer layer has different magnitudes in atleast one of laterally and vertically.
 16. An integrated-optical deviceaccording to claim 12, wherein the optical buffer layer comprises anembossed thermoplastic film.
 17. An integrated-optical device accordingto claim 12, wherein the optical buffer layer has a smaller layerthickness locally in a region opposite a sensitive window of thephotoelement.
 18. An integrated-optical device according to claim 12,wherein the optical buffer layer carrying the electrical conductortracks extends beyond the outer dimensions of at least one of the coverand base plates and has electrical contacts there.
 19. AnIntegrated-optical device in polymer technology, having a photoelementcoupled onto an optical waveguide, with only the evanescent fieldcomponents of the optical waveguide being coupled by an opticalintermediate element into the photoelement, and wherein: thephotoelement is incorporated into a polymeric upwardly closed coverplate; the cover plate is fitted exactly onto a base plate comprising apolymer layer having a light guiding optical waveguide; the intermediateelement is an optical buffer layer disposed between the cover plate andthe base plate; and a light entry surface of the photoelement isgeometrically closer to the optical waveguide than the cover plate andextends partially into the buffer layer.
 20. An integrated-opticaldevice according to claim 19, wherein the light entry surface is coveredby a semiconductor layer which has a higher refractive index than theoptical waveguide, and draws the evanescent light fields out of theoptical waveguide and feeds them to a light-sensitive junction of thesemiconductor layer for detection.
 21. An Integrated-optical device inpolymer technology, having a photoelement coupled onto an opticalwaveguide, with only the evanescent field components of the opticalwaveguide being coupled by an optical intermediate element into thephotoelement, and wherein: the photoelement is incorporated into apolymeric upwardly closed cover plate; the cover plate is fitted exactlyonto a base plate comprising a polymer layer having a light guidingoptical waveguide; the intermediate element is an optical buffer layerdisposed between the cover plate and the base plate; and the opticalwaveguide is produced in a base plate formed of organic polymer film;and the photosensitive side of the photoelement is adhesively attachedby a higher-refractive-index transparent adhesive, which forms thebuffer layer, directly onto the optical waveguide.
 22. Anintegrated-optical device according to claim 21, wherein-the degree ofoptical coupling is set by choice of the refractive index, the thicknessand the length of the polymer adhesive.
 23. An Integrated-optical devicein polymer technology, having a photoelement coupled onto an opticalwaveguide, with only the evanescent field components of the opticalwaveguide being coupled by an optical intermediate element into thephotoelement, and wherein: the photoelement is incorporated into apolymeric upwardly closed cover plate; the cover plate is fitted exactlyonto a base plate comprising a polymer layer having a light guidingoptical waveguide; the intermediate element is an optical buffer layerdisposed between the cover plate and the base plate; and the couplingdistance is set via spacers arranged between the polymer base platereceiving the optical waveguide and the photoelement.
 24. Anintegrated-optical device according to claim 23 wherein the spacers areformed by conductor tracks thickened by electroplating, applied to thephotoelement.
 25. An integrated-optical device according to claim 21,wherein the adhesive at the coupling location simultaneously serves tomechanically fix the photoelement to the base plate and waveguide. 26.An Integrated-optical device in polymer technology, having aphotoelement coupled onto an optical waveguide, with only the evanescentfield components of the optical waveguide being coupled by an opticalintermediate element into the photoelement, and wherein: thephotoelement is incorporated into a polymeric upwardly closed coverplate; the cover plate is fitted exactly onto a base plate comprising apolymer layer having a light guiding optical waveguide; the intermediateelement is an optical buffer layer disposed between the cover plate andthe base plate; and the optical waveguide is encapsulated together withthe coupled-on photoelement by a lower-refractive-index covering layer.27. An integrated-optical device according to claim 26 wherein thebuffer layer has a refractive index in a region opposite thephotoelement which is less than or equal to the refractive index of thebuffer layer outside the region opposite the photoelement.
 28. Anintegrated-optical device according to claim 1 wherein the buffer layerhas a refractive index in a region opposite the photoelement which isless than or equal to the refractive index of the buffer layer outsidethe region opposite the photoelement.
 29. An integrated-optical deviceaccording to claim 21, wherein the coupling distance is set via spacersarranged between the polymer base plate receiving the optical waveguideand the photoelement.